As is known by the man skilled in the art an electric dipole antenna is generally intended to receive the horizontal polarization (vertical polarization respectively when it is rotated by 90°) of transmitted radio signals when a magnetic dipole or a loop antenna is generally intended to receive the vertical (horizontal) polarization respectively of transmitted radio signals.
When wireless communication equipment is moving, the surroundings introduce what is usually named multiple signal paths (or multipaths).
For certain locations, these multiple signal paths induce a signal dropping, which involves a signal-to-noise ratio (SNR) lower than a chosen threshold. This situation frequently appears at several “fading” locations inside a room with classical dimensions. In these fading locations when the electric field is minimum, the magnetic field is generally maximum, and conversely.
To avoid this fading problem it has been proposed to introduce diversity in the antenna assembly. Such a diversity may be obtained by means of a combination of two antennas with different types.
Such a combination usually requires the antennas to be interspaced by a distance which is generally equal to λ/4, where λ is the signal wavelength. For small wireless communication equipment (such as mobile phones) with relatively low signal frequencies (such as the ones used in television transmissions), the requirement as regards the distance between the antennas cannot be respected.
Antenna structures such as PIFAs (Planar Inverted-F Antennas) or folded monopole or else loop antenna coupled to a ground plane have also been proposed. In these antenna structures a balanced current (resulting from a differential signal at the antenna entrance) and an unbalanced current (resulting from a common voltage between the antenna and the ground plane) are mixed (or superposed) together. In certain cases this current mixing is of interest, but for the purpose of diversity it would be preferable to extract the balanced and/or the unbalanced mode, as these modes have different behaviors towards fading.
So, the object of this invention is to improve the situation.